Hearing loss associated to brain shrinkage with age

A new study, published online on January 9th 2014 in the journal NeuroImage, suggests that older adults with impaired hearing may have a faster rate of brain shrinkage as they age.

Researchers at John Hopkins University, in Baltimore, and the National Institute on Ageing, looked at the on-going Baltimore Longitudinal Study of Ageing to compare the brains of older adults with normal hearing and those with impaired hearing. The Baltimore Longitudinal Study of Ageing started in 1958 by the National Institute on Ageing to monitor several health features in thousands of men and women.

The study focused on 126 adults aged from 56 to 86 years old who had yearly MRI brain scans for up to ten years. Fifty-one showed some degree of hearing loss, mostly mild to moderate; these people might have trouble hearing in a restaurant, for example. After analyzing participants MRIs over a decade, researchers found that the brains of those with impaired hearing shrank faster than the brains of those with normal hearing, and that the atrophy was concentrated in the parts of the brain related to hearing. Participants with impaired hearing lost more than an additional cubic centimeter of brain tissue each year.

Dr. Frank Lin, an assistant professor at Johns Hopkins University in Baltimore, and the lead researcher on the new study, says this research gives credence to the theory that “hearing loss is leading to changes in the brain structure or function.” As the saying goes, when it comes to muscles, use it or lose it. It seems that, in a similar way, if not used the part of the brain involved with hearing (as well as speech processing and memory) also begins to atrophy.

Dr. Frank Lin says the current theory is that hearing impairment does not directly cause dementia but that it may worsen problems in brain function. “It serves as another hit on the system, which could lead to an earlier expression of dementia,” he says.  But the “biggest question,” Lin said, is whether treating hearing impairment can slow changes in brain structure and, more importantly, delay dementia.

Dr. Frank Lin and his colleagues say they plan to eventually examine whether treating hearing loss early can reduce the risk of associated health problems, but results won’t be in for several years. For now, though, he recommends correcting hearing problems if at all possible.